Above-ground swimming pools have been used for many years and are popular, often preferred over permanent in-ground pools because of their low cost and portability. Typically, above-ground swimming pools include an outside metal frame with decking around the perimeter. The frame sets directly on the ground which is prepared to receive the frame and support the liner in the middle. The top of the frame holds a flexible liner which is supported on the bottom by the ground. Structural side walls of the pool are supported by the frame and also retain the liner.
Preparation of the ground area beneath the pool liner includes leveling the earth and then covering it with a loose substance that will evenly support the weight of the water-filled liner. Soft substances, such as peat moss, vermiculite or sand are commonly used as a fill material which is placed on the ground underneath the pool liner. The softness of this underlayment material protects the flexible pool liner from contact with sharp objects and will accept some deformation by a person standing on it so that tears and leaks from foot pressure are minimized.
These prior art underlayment materials, however, are less than ideal because problems with leaks still persist. The loose materials often settle or become washed out, and sharp stones underneath are often revealed which then tear the pool liner. The loose materials also do not fully protect against roots and weeds growing up through the material, which can similarly cause leaks. An additional problem is that the loose material often becomes wetted by ground water and retains this water along the area of the metal support frame, causing the frame to rust and corrode prematurely. Furthermore, the soft materials often retain foot print impressions made by occupants of the pool which detracts from the aesthetic appearance and desirability of having a smooth, flat, bottom surface. Finally, because above-ground pools are inherently shallow, there is a need for an underlayment which cushions swimmer impact. There is therefore a need in the art for an above-ground swimming pool underlayment system which solves these problems.